Title of Invention

A PROCESS FOR EXTRACTION OF POTASSIUM FROM FELDSPAR

Abstract

The invention relates to a process for the extraction of potassium from feldspar. The novelty of the invention resides in using mixture of magnesium sulfate and calcium carbonate in a definite proportion of 1:0.7-0.8:3 resulting into the 60-65 percent extraction of potassium into the solution. When feldspar is heated at 850-900 deg.C with calcium carbonate alone, recovery of potassium is only 10-12 % but by adding magnesium sulphate to calcium carbonate , the recovery of potassium increases upto 60 %.

Full Text

The present invention relates to a process for the extraction of potassium from feldspar. Potassium is a strategic metal, highly essential for agriculture as well as defence, both of which contribute to the progress of a country. But India with its vast agricultural base meets its entire requirement of potassium based fertilizer through import. Feldspar which contains about 13% of K2O is the most abundant rock forming mineral in nature and makes up an estimated 60% of earth's crust. India with its known recoverable sources of 16 million metric tons of feldspar produces less than 100,000 tons annually which is used mostly for glass and ceramic industiy. In the absence of primary source of potassium such as potassium bearing brine and underground deposits of soluble minerals in India, extraction of potassium from feldspar (orthoclase/microcline) is very significant. The present invention describes a method for extraction of potassium from feldspar of India. Reference may be made to U.S.Pat. 995,105 (1911) wherein an attempt was made by F. Thompson to extract potassium from feldspar by fusing it with sodium bisulphate and sodium chloride. Reference may be made to Bull. Inst. Mining Eng., 1(1917) wherein Ashcroft heated feldspar with sodium chloride alone in absence of air and moisture and proposed the following equation. 2 NaCl + K2O.Al2O3(Si02)6  Na2O.Al2O3(SiO2)6 + 2KC1. Reference may be made to U.S. Pat. 1,232,977 (1917) wherein Rhodin carried out the fusion in a reverberatory furnace along with mixture of SO2, steam and air. Reference may be made to U.S. Pat. 1,297,640 (1919) wherein feldspar was first heated at 535°C with excess NaNO3for 6-8 hr. Subssequent water leaching under pressure (4 atms) resulted in up to 80% yield Reference may be made to U.S. Pat. 1,125,007 (1915) and U.S. Pat. 1,160,171 (1916) wherein feldspar was heated with CaSO4 and CaCl2 to obtain soluble potassium salt. Reference may be made to Trans. Am. Ceram. Soc. 18,575 (1916) wherein Kirpatrick conducted fusion study on feldspar using calcite and magnesite. His studies indicated that feldspar was decomposed by CaO but not by MgO. Reference may be made to U.S. Pat. 1,310,413 (1914) wherein Eberhardt used 10-20% CaF2 as flux with 2-5% CaSO4 to bring down the calcination temperature. The drawbacks of the processes developed are that they involve sophisticated technology such as treating the ore with sulphur dioxide at higher temperature or leaching it under pressure or heating it with calcium fiouricle where the possibility of evolution of flourine gas is there. The processes developed so far aim at recovering potassium as potassium salt but the aim of the present invention is to bring potassium into solution and use it as a liquide fertilizer along with irrigation water. The process developed does not involve sophisticated technology. Work on extraction of potassium from feldspar continued in full swing till the end of first world war because countries like USA had not discovered their primary potassium source till that time, whereas Germany had a complete embargo over the potassium mines. But after the war primary sources of potassium were discovered in those countries. Hence researchers in those countries are not giving importance to extraction of potassium from feldspar. But conditions in India are different. The entire requirement of our potassium, may it be for agriculture or defence is met through import. When feldspar sample is heated at 850-900°C with calcium carbonate alone, recovery of potassium is only 10-12 percent. But addition of magnesium sulphate to calcium carbonate resulted in a remarkable increase in potassium recovery to the extent of about 60 percent conforming to the assumption that the reaction mechanism involved decomposition of calcium carbonate followed by formation of calcium silicate which enables the released potassium and aluminium to form water extractable sulphates. Similar results are also obtained when magnesium sulphate is replaced by calcium sulphate. The novelty of the invention is that neither calcium carbonate nor magnesium sulphate, when used alone can effectively attack the feldspar matrix but when a mixture of the two is used in a definite proportion, of 1:0.7-0.8:3, 60-65 percent of potassium is extracted into the solution. The main objective of this invention is therefore to establish a method for extraction of reasonably high amount of potassium from feldspar. Another objective of this invention is to utilize the vast feldspar deposits of India and reduce the import of potassium especially for fertilizer purpose. Still another objective of the present invention is to prepare a concentrated solution of potassium and magnesium from feldspar which may be used as a liquid fertilizer. Accordingly the present invention provides a process for the extraction of potassium from feldspar which comprises; powdering and sieving the feldspar sample through a sieve selected from 170, 240 and 400 mesh sizes, mixing the feldspar sample intimately characterized in that with magnesium sulphate arid calcium carbonate in the respective ratios of 1:0.7-08:3, drying the mixture at a temperature in the range of 115-125 deg.C for a period of 2 hrs, followed by cooling, powdering and mixing, roasting the said mixture at a temperature ranging from 850-900°C for a period of 5-6 hrs, cooling and refluxing it with required volume of water, filtering, concentrating and obtaining the desired product. In an embodiment of the present invention 10 grams of the feldspar sample is mixed and ground thoroughly with 7.5 grams of magnesium sulphate and 30 grams of calcium carbonate. In still another embodiment of the present invention the roasted mass is refluxed for about one hour with 500 ml of water. The essential steps of the process are as follows: a) Powdering and sieving the feldspar sample through sieves of mesh sizes 170,240 and 400. b) Mixing the feldspar sample, magnesium sulfate and calcium carbonate in the ratios of 1:0.75:3 intimately. c) Drying the mixture at 120°C for 2 hr. d) Cooling, powdering and mixing them again. e) Roasting the mixture at a temperature of 850-900°C for 5-6 hr. f) Cooling and refluxing them with required volume of water or 2hr. g) Filtering, concentrating and estimating potassium in the filtrate with the help of a flame photometer. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. Example -1 Feldspar sample obtained from Rajasthan was thoroughly powdered and sieved through 170 mesh. 10 grams of sieved sample with particle of 90 microns and less was mixed intimately with 7.5 grams of magnesium sulfate and 30 grams of calcium carbonate and dried at 120°C for 2 hr. It was cooled, powdered and roasted at 900°C for 6 hr. Then it was refluxed for 1 hr with 500 ml of water along with stirring in a 1 L capacity round bottom flask. It was cooled, filtered and potassium was measured in the filtrate with the help of a flame photometer. About 60 percent of potassium available in feldspar was extracted into the filtrate which can be concentrated and used as a liquid fertilizer. Example - 2 10 grams of feldspar sample (sieved through 240 mesh) having particle size of 63 microns and less was mixed intimately with 7.5 grams of magnesium sulphate and 30 grams of calcium carbonate and dried at 125°C for 2 hr. It was cooled, powdered and roasted at 900°C for 6 hr. Then it was refluxed with 500 ml of water along with stirring for one hour in a 1L capacity round bottom flask. It was filtered and potassium was measured in the filtrate with the help of a flame photometer. About 62 percent of potassium available in the feldspar was extracted into the filtrate which can be concentrated and used as liquid fertilizer. Example - 3 10 grams of feldspar sample of size 37 microns and less (sieved through 400 mesh) was mixed thoroughly with 7.5 grams of magnesium sulphate and 30 grams of calcium carbonate and dried at 125°C for 2 hr. It was cooled, powdered and roasted at 900°C for 6 hr. Then it was refluxed with 500 ml of water along with stirring in a 1L capacity round bottom flask for one hour. It was cooled, filtered and potassium was measured in the filtrate with the help of a flame photometer. About 65 percent of potassium available in the feldspar was extracted into the filtrate which can be concentrated and used as liquid fertilizer. The main advantage of the present invention are : 1. Development of a simple method for the extraction of potassium from a feldspar of India especially under the present scenario of the country when the total requirement of potassium is met through import. 2. The extracted solution containing potassium and magnesium (derived from the added magnesium sulphate) can be concentrated and used as a liquid fertilizer in stead of crystallizing potassium and magnesium salts from it. 3. The method once practised will reduce the import of potash since we will be able to tap the vast reserves of feldspar available in our country. 4. The steps described in the process do not involve stringent experimental conditions. ] We Claim: 1. A process for the extraction of potassium from feldspar which comprises; powdering and sieving the feldspar sample through a sieve selected from 170, 240 and 400 mesh sizes, mixing the feldspar sample intimately characterized in that with magnesium sulfate and calcium carbonate in the respective ratios of 1:0.7-0.8:3, roasting the mixture at a temperature ranging from 850-900°C for a period of 5-6 hrs, cooling and refluxing it with required volume of water, filtering, concentrating and obtaining the desired product. 2. A process as claimed in claim 1 wherein the roasted mass is refluxed for about one hour with 500 ml of water. 3. A process for the extraction of potassium from feldspar substantially as herein described with reference to the examples.

Documents:

163-del-2001-abstract.pdf

163-del-2001-claims.pdf

163-del-2001-correspondence-others.pdf

163-del-2001-correspondence-po.pdf

163-del-2001-description (complete).pdf

163-del-2001-form-1.pdf

163-del-2001-form-19.pdf

163-del-2001-form-2.pdf

163-del-2001-form-3.pdf